Among the maladies that continue to afflict man and other animals are tooth decay and tooth loss. Both of these afflictions have been subjected to much study and application of dental therapeutic measures with various rates of success. One aspect of dental therapy that has received attention is the understanding of, and attempts at overcoming, periodontal disease. Periodontal disease is a general term that encompasses diseases that affect the gingiva or supportive connective tissue and alveolar bone which anchors the teeth in the jaws. A particular periodontal disease that can occur in individuals is periodontitis where connective tissue such as periodontal ligament tissue is lost, alveolar bone is re-absorbed, and periodontal pockets are formed. In more advanced stages of such a periodontal disease, teeth become loosened and may eventually be lost because of the compromised surrounding support structure. As the disease progresses, a gingival pocket which previously formed becomes deeper, and the alveolar bone is destroyed and absorbed. If this condition is left untreated, the affected tooth loses structural support and may fall out. With recent advancements in the treatment/prophylaxis of dental caries and the demographic movement towards an aging society, periodontal disease has attracted increased attention and its treatment has become an important subject. Severe periodontal disease requires reconstruction of the periodontal tissue by a surgical procedure. Its purposes are not only to remove the periodontal pocket but also to recover occlusive function through regeneration of the periodontal tissue destroyed by periodontal disease. Treatment of lost gum and bone tissue is challenging in the best case. For example, a representative corrective surgical technique currently performed is the gingival flap operation. However, postoperative recovery including true attachment accompanied by neogenesis of the cementum of the new attachment is typically limited only to the apical region, and ideal epithelial attachment is not achieved in other regions.
Periodontal diseases including periodontitis are caused by an accumulation of bacteria on the surface of the tooth and under the gingiva. Specific microorganisms that have been suggested as causative agents of periodontal disease are Actinobacillus actinomycetemcomitans, Bacteroides forsythus, Campylobacter rectus, Eikenella corrodens, Fusobacterium nucleatum ss vincentii, Peptostreptococcus micros, Porphyromonas gingivalis, Prevotella denticola, Prevotella intermedia, Prevotella nigrescens, Streptococcus intermedius, Treponema denticola, Tannerella forsythia, Campylobacter gracilis and Actinomyces viscosus. Mixtures of two or more microbial species may be present and cause, either individually or synergistically, periodontal disease.
Elimination of bacterial infection is key to the successful treatment of periodontal disease. It has been known for some time that silver compounds exhibit antimicrobial activity, which is known as the oligodynamic effect as discovered in 1893 by Karl Nageli. Silver sulfadiazine, when applied topically to the supra-gingival tooth surface in a gel base, has been shown both to prevent and to reduce gingival inflammation and plaque formation in beagle dogs (T. H. Howell et al., J. Periodontal Res. 25:197-200 (1990) and T. H. Howell et al., J. Clin. Periodontal. 17: 734-737 (1990)). Potential drawbacks to using silver compounds supra-gingivally in the treatment of periodontal disease are the staining of teeth and oral mucosa and the unpleasant taste that such treatment engenders. A potent, microbiocidally effective formulation that is locally applied subgingivally would provide a significant improvement in the treatment of periodontal disease.
U.S. Pat. No. 6,153,210 describes another treatment method for periodontal disease which uses metallic ionic compounds formed from silver chemically bonded to bromine, fluorine, chlorine, and others, to form any of the various compounds silver acetate, silver bromate, silver chlorate, silver perchlorate, silver chlorite, silver fluoride, silver lactate, silver permanganate, silver protein, silver nitrate, silver nitrite, silver sulfadiazine, silver sulfate or combinations of these chemical compounds and complexes. Of these chemical compounds and complexes, it is suggested in this patent that silver nitrate, silver chlorate, silver perchlorate and silver fluoride are preferred.
One of the problems in the delivery of metal ions at the chemical level is an interaction between the surface charge of the bacteria and the suspended metal ions, and this interaction causes a variation in the local concentration of metal ions. In particular, if the particular bacteria colony operative in the periodontal disease has a surface charge which is the same polarity as the naturally occurring positive ionic potential of the metal ions, the local concentration of the metallic ions in the area surrounding the bacteria will be reduced. It is desired to provide an apparatus for generation of aqueous solutions of nanoparticles of silver, copper, and iron, and in an optimum size range for use in treatment of periodontal disease. It is also desired to provide a method for application of nanoparticles for treatment of periodontal disease.